Aider Engine

The open-source AI pair programmer. Aider works directly with your git repository, makes atomic commits, and supports a vast range of LLM backends — all surfaced through QuantumReef's unified interface.

Overview

Aider is a command-line AI coding assistant that operates as a first-class git citizen. Every change Aider makes is committed to your repository with a descriptive message — giving you a complete, reviewable history of AI-assisted work. QuantumReef wraps Aider via its --no-pretty --json flags, capturing its structured output into the standard session UI.

Aider's whole-repository map feature (repo map) gives the LLM a compressed, token-efficient representation of your entire codebase, enabling accurate edits even in projects with thousands of files — without needing to load every file into context.

Best for git-native workflows

If your team treats the git log as a first-class artefact and wants every AI change to be reviewable, revertable, and attributed, Aider is the right engine. Its commit discipline is unmatched among AI coding tools.

How Aider Integrates with QuantumReef

QuantumReef's AiderClient adapter launches Aider as a subprocess in non-interactive mode, passing each prompt via stdin and reading the structured JSON response from stdout. Key integration points:

File edits are shown in QuantumReef's diff viewer before being committed
Git commits made by Aider appear in the Session Timeline with hash and message
The repo map is recomputed automatically when files change between prompts
Aider's /undo command is bound to QuantumReef's session undo button
Multi-file edits show a consolidated diff across all changed files

Installation

Install Aider

bash

# Install via pip (recommended)
pip install aider-chat

# Or via pipx (isolated environment)
pipx install aider-chat

# Or via Homebrew on macOS
brew install aider

# Verify
aider --version

Set up API keys

bash

# Anthropic Claude (best results with Aider)
export ANTHROPIC_API_KEY=sk-ant-...

# OpenAI
export OPENAI_API_KEY=sk-...

# DeepSeek (cost-effective alternative)
export DEEPSEEK_API_KEY=sk-...

# Local Ollama (no API key needed)
# Start Ollama first: ollama serve

Enable in QuantumReef

Go to Settings → Engines → Aider and toggle on. QuantumReef will locate the aider binary in your PATH. If you use a Python virtual environment, set the absolute path to the binary in Settings.

Git Integration

Aider's git integration is its defining feature. Every prompt that modifies files results in one or more git commits. QuantumReef surfaces this workflow in the Session Timeline panel:

Feature	Description
Auto-commit	Aider commits each edit with a message like 'feat: add pagination to UserList'
Atomic commits	Related file changes are grouped into a single commit
Undo last commit	Session undo button runs `git reset HEAD~1` inside Aider's session
Dirty check	Aider warns if your working tree has uncommitted changes before starting
Branch awareness	QuantumReef shows the current branch in the session header

Work on a feature branch

Aider commits directly to the current branch. Always start an Aider session on a dedicated feature branch so you can review, squash, or revert AI-generated commits before merging.

Configuration

Aider Config File

.aider.conf.yml

# Model selection
model: claude-opus-4-5
# Fallback for cheaper tasks
weak-model: claude-haiku-3-5

# Repo map settings
map-tokens: 2048
map-refresh: auto

# Auto-commit behaviour
auto-commits: true
dirty-commits: false
commit-prompt: "Conventional commits format"

# Linting (auto-fix on each edit)
lint: true
lint-cmd: "eslint --fix {files}"

# Test runner (auto-run after edits)
test: false
test-cmd: "pnpm test --run"

QuantumReef Engine Settings

Setting	Default	Description
Model	claude-opus-4-5	Primary model for edits
Weak Model	claude-haiku-3-5	Used for repo map and simple tasks
Auto Commits	true	Commit after every successful edit
Map Tokens	2048	Tokens reserved for the repository map
Edit Format	udiff	How Aider requests edits: udiff, diff, whole
Watch Files	false	Aider watches files for changes and asks to add them

Repository Map

Aider's repo map is a compressed, CTags-derived summary of your entire codebase. It tells the LLM about all classes, functions, and their call sites without loading every file in full. This enables accurate, cross-file edits in large codebases.

bash

# View the repo map Aider would send (useful for debugging)
aider --show-repo-map

# Increase map size for larger projects (more tokens, better accuracy)
aider --map-tokens 4096

# Exclude directories from the map
echo "vendor/" >> .aiderignore
echo "node_modules/" >> .aiderignore
echo ".next/" >> .aiderignore

When to Choose Aider

Use Case	Why Aider Excels
Git-native teams	Every change is a reviewable, revertable commit
Large existing codebases	Repo map provides whole-project awareness without loading all files
Multi-model experimentation	Switch between 20+ LLM providers with a single config change
Linting/testing loops	Auto-lint and auto-test after each edit closes the feedback loop
Cost-conscious teams	DeepSeek and Ollama backends offer near-zero cost operation